Device for replacing safety plugs of steam boilers



April 15, 1930.

c. H. SWEET ET AL 1,754,657 DEVICE FOR REPLACING SAFETY PLUGS 0F STEAM BOILERS Filed Feb. 8, 1928 l I l "Zia 51v TORS, CfCJL .19: 5 1 /55 7- Eon 1 Fawkes r Hans 7- 44 r roam 5K Patented Apr. 15, 1930 UNITED OFFECE CECIL H. SWEET AND EDWIN FORREST HUB/ST, OF BREA, CALIFORNIA.

DEVICE FOR REPLACING SAFETY PLUGS OF STEAM BOILERS Application filed February 8, 1928. Serial No. 252,928.

This invention relates to safety devices for steam boilers, and more particularly stated is for means for replacing fusible plugs where employed as a safety measure in case the water in the boiler falls too low.

A common modern practice is to provide the crown sheet of a boiler with a fitting or retainer in which a fusible plug is received, the plug being adapted to melt in the event that the water level falls below the plug and allows the crown sheet to heat up unduly. When the plug does melt the steam then blows out through the fitting into the boiler and quenches the fire, and heretofore, before the 1 boiler could be used again, it has been necessary to wait for several hours for the firebox to cool down sufliciently to allow a workman to enter and replace the plug.

It is the object of the present invention to provide a structure by means of which a new plug may be immediately inserted in the fitting in place of the one which melted, thereby saving the large amount of time heretofore wasted in waiting, and also saving the heat heretofore lost in allowing the boiler and firebox to cool, a large part of which heat was represented in steam which ordinarily continued to form by reason of the residual heat in the plant and which heretofore escaped.

Briefly stated, the invention resides in a guide fitted into the boiler and projecting from the exterior thereof into position adj acent the plug-retaining fitting in the crown sheet, the guide being of perforate formation within the boiler to admit steam to the fitting, but being imperforate exteriorly of the boiler to hold steam against escape, said guide being provided exteriorly of the boiler with a valve for the passage of a reaming tool and of a new plug. The guide may be a tube and the valve a gate valve, and in a preferred form the tube is further provided with a stuifing box passing the stem of a reamer, and with a branch carrying another gate valve for initial introduction of a new plug. The invention resides further in such other novel features of construction and combination as may be herein presented.

In the accompanying drawings wherein one embodiment of the invention is disclosed by way of illustration;

Fig. 1, is an elevation of a boiler and its mounting, portions being broken away to show the installation of the present invention thereon.

Fig. 2, is an enlarged sectional detail through the device as indicated by line 22 of Fig. 1.

Fig. 3, is a further enlarged detail showing the construction of the plug-retainer to insure proper seating of the plug when dropped into the guide.

These drawings show the usual boiler shell 10 and the crown sheet 12 which receives a plug-retaining fitting 14 threaded thereinto and provided with a passage 15 whose upper end is tapered to form a seatfor a fusible plug 16 pressed into position to prevent the escape of water or steam through passage 15. As best seen in Fig. 3, the upper edge of this retainer is tapered or narrowed sufficiently to prevent catching of the lower end of the plug thereupon when the plug is dropped from above, and thereby to insure proper seating of the plug. Said fitting 14 is shouldered at 18 to receive the lower end of a perforated guide 20 whose upper end threaded into an imperforate tube 22 located exteriorly of the boiler but secured therein as by $9 threading at 23. The upper end of the tube is provided with a gate valve 24 which may be opened to pass a reamer and a new plug 16 when replacement of the plug is required.

However, in order to protect the workman againstescaping steam and also to conserve the steam, a second section of tube 25 having a branch 26 may be provided, the branch being equipped with a second gate valve 28 for 99 the initial introduction of the plug, while the upper end of the main length of tube 25 is provided with a stuffing box 30 through which passes the stem 32 of a reamer 3e operable exteriorly by means of hand wheel 35 or the like. I

When the boiler is in normal operation the gate valve 24 is closed to prevent passage of steam, and the plug 16is secured in position in fitting 1d, the perforations in tube 20 permitting access of water to the plug. lVhen the water falls too low and thereby produces a dangerous condition, the plug 16 immediate- 1y heats up and melts, thus permitting the steam to blow through the passage and quench the fire and cool the firebox somewhat. However, it is not necessary to wait now for the firebox to cool. On the other hand, after insuring that the gate valve 28 is closed, the valve 24 is opened and the reamer 3 1 is run down to the seat of retainer 14 and any fused metal on the seat is removed. The reamer 34: is then withdrawn into the upper end of the tube section and valve 24 is closed. A new plug 16 is then dropped into the branch 26 by opening valve 28, valve 38 being then closed again. The plug falls upon the gate of the valve 24, but the proportions of the plug are such that it maintains a sufficiently upright position and cannot turn over. Upon opening valve 2st, the new plug drops into the seat in fitting 14. The reamer is then run down and used as a tool to drive the plug firmly into its seat. The boiler is now ready to be again filled with water and fired.

From the foregoing it will be noted that the valve 24 prevents loss of steam during normal operation of the boiler, and that, when a new plug is being placed, the stuffing box and valve 28 prevent the escape of any steam remaining in the boiler or being formed by the residual heat. This not only protects the workman but conserves heat in the form of steam. Thus, the work of replacing the plug and getting the boiler back into operation, is speeded up, and only a very few min utes are lost in the entire replacement operation.

e claim:

1. The combination with a boiler and its crown sheet, of a bushing constituting a plug seat fitted in an opening in the crown sheet and a lower tube provided with openings in its wall and having its lower end engaging the bushing and extending through the steam and water space of the boiler to the exterior thereof, a second tube secured to the upper end of said lower tube provided at its upper end with a stuffing box, a reamer rod passing through the stufiing box for reaming the bushing seat, a valve intermediate the ends of said second tube, and a valve controlled conduit leading to said second named tube above its valve for guiding a plug into the second named tube, whereby the plug may be seated in the bushing on a manipulation of the valves without removing any parts of the mechanism.

2. The combination with a boiler and its crown sheet, of a bushing constituting a plug seat fitted in an openin in the crown sheet and a lower tube provided with openings in its wall and having its lower end engaging the bushing and extending through the steam and water space of the boiler to the exterior thereof, a second tube secured to the upper end of the lower tube and provided with a valve on its upper end, and a Y fitting having a vertical branch secured to said valve and extending upwardly therefrom, the vertical branch "0 of said fitting being provided at the upper end with an opening for the passage of a reamer rod therethrough, a reamer rod disposed in the opening of the vertical branch of the fitting, the other branch of said fitting bein provided with a valve closure.

3. The combination with a boiler and its crown sheet, of a bushing constituting a plug seat fitted in an opening in the crown sheet and a lower tube provided with openings in its wall and having its lower end engaging the bushing and extending through the steam and water space of the boiler to the exterior thereof, a second tube secured to the upper end of the lower tube and provided with a valve on its upper end, a Y fitting having a vertical branch secured to said valve and extending upwardly therefrom, the vertical branch of said fitting being provided with a stuffing box and the other branch of said fitca ting being provided with a valve closure, and a rod provided with a reamer on its lower end disposed in the vertical branch of the Y fitting and extending outwardly through said stuffing box. or,

In testimony whereof we afiix our signatures.

CECIL I-I. SVEET. EDXVIN FORREST HURST. 

